Certified Rhythm Analysis Technician (CRAT) Practice Exam

For an ECG machine, the sweep speed is critical in interpreting the heart's rhythm accurately. The standard is typically set at 25 mm per second for many ECG machines. At this speed, each 1 mm on the ECG paper represents 40 milliseconds, meaning that if you have a sweep speed of 25 mm per second, you're able to cover 1000 milliseconds (or 1 second) across 25 mm of paper.

To achieve a scenario where 1 mm equals 400 milliseconds, you consider how quickly the machine needs to move the paper. When the speed is set to 25 mm per second, you multiply that speed by the duration represented by each millimeter. Therefore, if each mm equals 40 milliseconds at 25 mm per second, it can be deduced that the equivalent time in milliseconds for a larger distance on the paper increases as the speed decreases.

Consequently, at 25 mm per second, 1 mm corresponds to 400 milliseconds, as the slower the machine records the rhythm, the more time is represented over the same distance on the paper. This makes understanding the sweep speed essential for accurate rhythm interpretation and diagnosis.